<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width"/>
    <style type="text/css">
        body {
            height: 100vh;
        }
        .wrapper {
            height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
        }
    </style>
</head>
<body>
<div class="wrapper">
    <h3>我的第一个Web页面，欢迎进入！</h3>
</div>
</body>
</html>